Oscillatory and steady shear rheology of gellan/dextran blends

Oscillatory and steady shear rheology of gellan (G) and dextran (D) solution individually, and in blends (G/D ratio 1:1, 1:2, and 1:3 w/v) with a total hydrocolloid concentration of 3 % (w/v) were studied at 25 A degrees C. Individually, 1.5 % dextran and 1.5 % gellan in solution exhibited Newtonian and non-Newtonian behavior, respectively. A blend of equal proportion of dextran and gellan (G/D = 1:1) exhibits a distinct gel point (G' = GaEuro(3)), and further addition of dextran in the blend (G/D = 1:2 and 1:3) resulted predominating liquid-like (GaEuro(3) > G') behavior. A plot of G' vs GaEuro(3) distinctly showed the gradual transition of the blend. Shear stress (tau)-shear rate () data fitted well the Herschel-Bulkley model. The G/D blend exhibited shear thinning behavior with flow behavior index less than unity. The Cox-Merz rule did not fit well for the complex shear viscosity (eta*) and apparent viscosity (eta) of the blend.